Comparison of the membrane glycoproteins of control and malignant cells has revealed a difference in their bound carbohydrate groups. The difference which occurs in the sugar groups of over 80% of the glycoproteins in all of the membrane systems of the cell is very widespread, occurring in five species of cells in solid tumors and malignant cells in culture. The significance of this finding is unknown because aside from a few well known dramatic examples of involvement of bound sugars in specific function, the basic role of bound sugars is not really known. We have formulated a hypothesis which may answer the question why proteins bear carbohydrates and what the significance of structural changes could be. Experiments that may provide some answers to this question of protein-bound carbohydrate are proposed. The effects of changing the environment of cells (medium, pH, temperature, etc.) on the bound carbohydrates of the glycoproteins is being investigated. The functional consequences of changes in bound carbohydrate will be studied. We are continuing with comparative structural studies of protein-bound carbohydrates of control and transformed cells. The underlying basis for the change of glycoprotein carbohydrates in malignancy is being investigated at the enzyme level.